This invention relates to an electronic, thermally sensitive switch device responsive to an ambient temperature in excess of a predetermined magnitude to perform the switching operation.
Heretofore, there have been widely employed switches including metallic contacts such as bimetal switches, mercury thermostat switches etc. Those switches have encountered problems in wear and tear and chattering of the contacts, transient voltages and impulsive sound developed upon switching, low switching speeds etc. As a result, such switches have limited application as a thermally sensitive switch. On the other hand, there are known thermistors which act as a thermally sensitive resistance element and also thermally sensitive switches utilizing a thermistor. Since the thermistor itself has no ability to turn currents on and off, it has been required to operatively associate the thermistor with resistors to form a resistance bridge having the thermistor disposed on one arm thereof, while the resistance bridge is electrically connected to a differential amplifier subsequently coupled to a transisterized switch. This has led to the disadvantages that the resulting devices are complicated in construction and become expensive.